1. Field of the Invention
The present invention relates to a semiconductor device, particularly a semiconductor device provided with a polycrystalline silicon resistor in which trimming is possible.
2. Description of the Related Art
It is known from "Technical Report SSD79-16" issued by the Institute of Electronic Communication (1979) that the resistance of a polycrystalline silicon resistor containing a large amount of impurities is adjustable by conducting an electric current therethrough at a current density of a threshold value or more, and that the polycrystalline silicon resistor must contain an impurity at a concentration of 10.sup.20 cm.sup.-3 or more.
In a high precision integrated circuit (IC), such a polycrystalline silicon resistor also serves as a high precision standard resistor and must have a temperature coefficient of resistance (TCR) of zero. Nevertheless, a problem arises in that the zero TCR value cannot be obtained in an impurity concentration region in which trimming is possible, and thus a conventional trimmable polycrystalline silicon resistor of a high precision IC cannot simultaneously have both a zero TCR value and a good trimming property, i.e., a high rate of resistance change.